I am currently studying the textbook Light-Emitting Diodes (3rd Edition) by E. Fred Schubert. Chapter 2.1 Compound semiconductors says the following:

In 1874, Karl Ferdinand Braun (1874), a German scientist, reported on the electrical conduction in metal-semiconductor structures where the semiconductor was a metal sulfide such as ZnS, PbS, FeS$_2$, and CuFeS$_2$. He found that the current-voltage characteristic was asymmetric and non-ohmic and thus exhibited some degree of rectification. His work is the first demonstration of the rectifying properties of metal-semiconductor contacts and the first scientific research in compound semiconductors.

What is meant by "the current-voltage characteristic was asymmetric and non-ohmic", and why does this mean that the semiconductor exhibits some degree of rectification?


1 Answer 1


Ohmic would mean means it follows Ohm's law $\ I= {\mathcal{E} \over R} $

It's non-ohmic so it does not, the current passed is not proportional to the EMF.

Symmetric would mean that for negative EMF the the exact opposite current would flow. Being asymmetic, (in this case) it means that current flows more readily in one direction than in the opposite direction (this detail is given in the explanation).

  • $\begingroup$ Thanks for the answer. So how is the rectification part relevant to this? $\endgroup$ Feb 4, 2021 at 4:14
  • 2
    $\begingroup$ Recticfiers (diodes) conduct better in one direction than they do in the other, exactly like the devices he's describing... lead suphide (galena) actually found a use in electronics as the crystal in some early crystal sets. $\endgroup$
    – Jasen
    Feb 4, 2021 at 4:51

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